Such door actuating devices are well known and are likewise designated as door drives or as door closers. A distinction should be made, in particular between door actuating devices comprising an electro-hydraulic unit, which also allow for opening the doors via the door actuating device, whereas devices without an electro-hydraulic drive simply control the kinematics of the door closing movement. The known door actuating devices have in common that they include a spring energy accumulator, which, in the form of mechanical work, stores the energy required for the closing movement of the door. In this case, storing the mechanical work is realized by means of at least one spring, which is preferably configured as a compression spring, which is tensioned during the opening movement of the door. The compression spring relaxes during a closing movement of the door, whereby the stored mechanical work, in the form of energy, is released and effects the closing movement of the door.
The door actuating devices may be either inserted into the door frame or incorporated into the door leaf itself. When utilizing the known door actuating devices in fire-rated doors, minimum closing moments of the doors need to be achieved, wherein these moments depend on the width and the weight of the doors. In this case, requirements are to be respected, which relate for example to the availability of energy mechanically stored in the door actuating devices, such that a fire-rated door autonomously executes a closing procedure of the door even in the event of power failure and thus in the event of a possible control failure of the door actuating device. In order to create uniform actuating devices of the door leaves for a plurality of variants of different door widths and door weights, spring adjusting devices are provided by means of which the initial tensile force of the compression spring can be adjusted, which spring stores the mechanical energy to provide a minimum closing momentum of the door leaf.
A spring adjusting device is known from the utility model DE 92 09 276 U1, which comprises a supporting ring on which the end side of the compression spring rests. The supporting ring has a female thread into which a spring adjusting device is screwed, wherein the spring adjusting device is disposed to be axially fixed in a closing screw at the end side of the housing of the device. By rotating the spring adjusting device, the supporting ring is caused to move axially, such that the compression spring is compressed, respectively relaxes. In this case, the supporting ring is able to rotate, as long as it is not axially guided in a complex manner inside the housing via corresponding guiding grooves.
A door closer with an adjustable closing force is known from the document DE 32 24 300 C2. This door closer comprises at least one compression spring disposed in the closer housing and bearing with one end against an adjustable plate, and a device for adjusting the plate which can be actuated from outside the housing. In this case, the plate is disposed on a rotatably supported and drivable threaded spindle, wherein the spring plate, disposed on a threaded spindle, is driven via a worm gear. This complex configuration, in particular the worm gear requires considerable space, because a drive worm, which is disposed tangentially with regard to the worm wheel, cannot be incorporated into a small installation space.
Therefore, the known state-of-the-art is disadvantageous in that the embodiments for spring force adjusting devices require enormous installation space on the one hand, such that a narrow built embodiment of a door actuating device is not possible in order to incorporate the latter preferably into a door leaf or, in more general terms, into a location where only a very limited installation space is available. On the other hand, the known door actuating devices require considerable technical expense in terms of manufacturing.